Purchased in sets. When there are many books on hand at the actual work site size notation is hard to understand and it is hard to understand! I want you to write large numbers like color coding or other company's products. Although it is easy to use with respect to thickness, there are also rare ball push thought that this is thick. The point which is particularly superior to other companies' product is the length of the pattern. It is not too long, it is not too short, and fine adjustment is possible.